Generally, the widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball device, or the like. Via the keyboard device, characters or symbols can be inputted into the computer system directly. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboard devices.
The structures and the functions of a conventional keyboard device 1 will be illustrated as follows. Please refer to FIGS. 1, 2 and 3. FIG. 1 is a schematic top view illustrating the outer appearance of a conventional keyboard device. FIG. 2 is a schematic exploded view illustrating a portion of the keyboard device of FIG. 1 and taken along a viewpoint. FIG. 3 is a schematic exploded view illustrating a portion of the keyboard device of FIG. 1 and taken along another viewpoint. For succinctness, only one key 10′ and related components are shown in FIGS. 2 and 3.
The conventional keyboard device 1 comprises plural keys 10 and 10′, a base plate 11 and a membrane circuit board 12. Each of the plural keys 10 and 10′ comprises a keycap 101, a scissors-type connecting element 102 and an elastic element 103. The scissors-type connecting element 102 is connected between the keycap 101 and the base plate 11. Moreover, the scissors-type connecting element 102 comprises a first frame 1021 and a second frame 1022. The second frame 1022 is pivotally coupled to the first frame 1021. Consequently, the first frame 1021 and the second frame 1022 can be swung relative to each other. The elastic element 103 is arranged between the keycap 101 and the base plate 11. Moreover, the elastic element 103 comprises a contacting part 1031.
FIG. 4 is a schematic exploded view illustrating the membrane circuit board of the keyboard device as shown in FIG. 1. The membrane circuit board 12 comprises an upper film layer 122 and a lower film layer 123. A first circuit pattern 1221 is formed on a bottom surface of the upper film layer 122. The first circuit pattern 1221 comprises plural upper contacts 1222 corresponding to the plural keys 20 and 20′. A second circuit pattern 1231 is formed on a top surface of the lower film layer 123. The second circuit pattern 1231 comprises plural lower contacts 1232 corresponding to the plural upper contacts 1222. Each of the upper contacts 1222 and the corresponding lower contact 1232 are separated from each other by a spacing interval. Moreover, each of the upper contacts 1222 and the corresponding lower contact 1232 are collectively defined as a membrane switch 121. Moreover, for maintaining the spacing interval between each upper contact 1222 and the corresponding lower contact 1232, the membrane circuit board 12 further comprises an intermediate film layer 124. The intermediate film layer 124 is arranged between the upper film layer 122 and the lower film layer 123. In addition, the intermediate film layer 124 comprises plural perforations 1241 corresponding to the plural upper contacts 1222 and the plural lower contacts 1232.
While the keycap 101 of any key 10 or 10′ is depressed and moved downwardly relative to the base plate 11, the first frame 1021 and the second frame 1022 of the scissors-type connecting element 102 are switched from an open-scissors state to a stacked state. Moreover, as the keycap 101 is moved downwardly to compress the elastic element 103, the corresponding membrane switch 121 is pushed and triggered by the contacting part 1031 of the elastic element 103. Consequently, the keyboard device 1 generates a corresponding key signal. When the keycap 101 of the key 10 or 10′ is no longer depressed, the keycap 101 is moved upwardly relative to the base plate 11 in response to an elastic force of the elastic element 103. Meanwhile, the first frame 1021 and the second frame 1022 are switched from the stacked state to the open-scissors state again, and the keycap 101 is returned to its original position.
Please refer to FIGS. 1, 2 and 3 again. As shown in the drawings, the length L1 of the key 10′ is larger than the width W1 of the key 10′. The key 10′ further comprises a first stabilizer bar 104 and a second stabilizer bar 105. The first stabilizer bar 104 comprises a first transverse bar part 1041 and two first hook parts 1042. The two first hook parts 1042 are located at two ends of the first stabilizer bar 104, respectively. The second stabilizer bar 105 comprises a second transverse bar part 1051 and two second hook parts 1052. The two second hook parts 1052 are located at two ends of the second stabilizer bar 105, respectively.
The base plate 11 comprises a first connecting structure 111 and a second connecting structure 112. The first connecting structure 111 and the second connecting structure 112 are protruded upwardly, and penetrated through the membrane circuit board 12. The first connecting structure 111 comprises a first locking hole 1111 and a third locking hole 1112. The second connecting structure 112 comprises a second locking hole 1121 and a fourth locking hole 1122. The second locking hole 1121 corresponds to the first locking hole 1111, and the fourth locking hole 1122 corresponds to the third locking hole 1112.
The first transverse bar part 1041 of the first stabilizer bar 104 and the second transverse bar part 1051 of the second stabilizer bar 105 are pivotally coupled to the keycap 101 of the key 10′. The two first hook parts 1042 of the first stabilizer bar 104 are penetrated through the first locking hole 1111 of the first connecting structure 111 and the second locking hole 1121 of the second connecting structure 112, respectively. The two second hook parts 1052 of the second stabilizer bar 105 are penetrated through the third locking hole 1112 of the first connecting structure 111 and the fourth locking hole 1122 of the second connecting structure 112, respectively.
FIG. 5 schematically illustrates the actions of the first stabilizer bar and the second stabilizer bar of the keyboard device as shown in FIG. 1. While the keycap 101 of the key 10′ is moved upwardly or downwardly relative to the base plate 11, the first stabilizer bar 104 is moved in the direction D11 or the direction D12 and rotated in the direction D13 or the direction D14. Similarly, the second stabilizer bar 105 is moved in the direction D11 or the direction D12 and rotated in the direction D13 or the direction D14. By this design, the key 10′ is kept stable and not inclined while the key 10′ is moved upwardly or downwardly relative to the base plate 11. Moreover, this design is helpful to increase the strength of the keycap 101.
However, the conventional keyboard device 1 still has some drawbacks. For example, all of the first stabilizer bar 104, the second stabilizer bar 105 and the base plate 11 are made of metallic material. Please refer to FIG. 5. While the keycap 101 of the key 10′ is moved upwardly or downwardly relative to the base plate 11 and the first stabilizer bar 104 and the second stabilizer bar 105 are correspondingly moved and rotated, the two first hook parts 1042 of the first stabilizer bar 104 and the two second hook parts 1052 of the second stabilizer bar 105 are readily contacted with the metallic base plate 11. While the two first hook parts 1042 and the two second hook parts 1052 collide with the metallic base plate 11, a click sound is generated. This sound is unpleasant noise to the user.
For solving the above drawbacks, another conventional keyboard device was disclosed. FIG. 6 is a schematic perspective view illustrating a membrane circuit board of another conventional keyboard. FIG. 7 is a schematic cross-sectional view illustrating the membrane circuit board of FIG. 6 and taken along the line A-A. FIG. 8 schematically illustrates the actions of the first stabilizer bar and the second stabilizer bar of another conventional keyboard device. In comparison with the keyboard device of FIG. 1, the keyboard device as shown in FIGS. 6, 7 and 8 are distinguished by the following items. Firstly, the lower film layer 123′ of the membrane circuit board 12′ further comprises a first extension part 1233 and a second extension part 1234. The first extension part 1233 and the second extension part 1234 are extended toward the first connecting structure 111 and the second connecting structure (not shown). The two first hook parts 1042 of the first stabilizer bar 104 are separated from the base plate 11 by the first extension part 1233. The two second hook parts 1052 of the second stabilizer bar 105 are separated from the base plate 11 by the second extension part 1234. While the keycap 101 of the key 10′ is moved upwardly or downwardly relative to the base plate 11 and the first stabilizer bar 104 and the second stabilizer bar 105 are correspondingly moved and rotated, the two first hook parts 1042 of the first stabilizer bar 104 and the two second hook parts 1052 of the second stabilizer bar 105 are respectively moved on the first extension part 1233 and the second extension part 1234. Since the two first hook parts 1042 and the two second hook parts 1052 are not directly contacted with the base plate 21, the two first hook parts 1042 and the two second hook parts 1052 do not collide with the base plate 11 to generate the unpleasant noise.
Nowadays, the trends of designing keyboard devices are designed toward small size, light weightiness and easy portability. Consequently, each film layer of the membrane circuit board becomes thinner and thinner. As mentioned above, the first extension part is extended from the lower film layer and arranged between the two first hook parts of the first stabilizer bar and the base plate, and the second extension part is extended from the lower film layer and arranged between the two second hook parts of the second stabilizer bar and the base plate. Under this circumstance, the efficacy of reducing the noise by the first extension part and the second extension part is largely reduced.
In other words, the conventional keyboard device needs to be further improved.